1. Field of the Invention
The present invention relates to a mechanism usable for signaling buffer status information for communication over licensed and unlicensed spectrum. In particular, the present invention is related to apparatuses, methods and computer program products providing a mechanism by means of which buffer status information can be signaled to the network wherein communication resources in licensed and unlicensed spectrums are considered, in particular in an offloading case where traffic is offloaded from a transmission via one spectrum to a transmission via another spectrum.
2. Related Background Art
Prior art which is related to this technical field can e.g. be found by the technical specification 3GPP TS 36.321, for example according to version 10.2.0.
The following meanings for the abbreviations used in this specification apply:    ABS: actual buffer size    BS: base station    BSR: buffer status report    D2D: device-to-device    DL: downlink    eNB: enhanced node B    EGTA: estimated offloading traffic amount    ISM: industrial, scientific and medical    LTE: Long Term Evolution    LTE-A: LTE Advanced    LS: licensed spectrum    MAC: medium access control    NM: normal mode    OM: offloading mode    RB: radio bearer    RBG: radio bearer group    RRC: radio resource control    VBS: virtual bearer size    UE: user equipment    UL: uplink    UL-SCH: uplink shared channel    US: unlicensed spectrum
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), enhanced communication networks based e.g. on LTE, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.
Recently, so-called “proximity-based” applications and services came into the focus of further developments in the field of telecommunications. The term proximity-based applications and services may be used, for example, in cases where two or more devices (i.e. two or more users), which are close to each other, are interested in exchanging data, if possible, directly with each other.
Currently, such “proximity-based” applications operate fully “over the top” and are based on “high-level software”, typically relying on a mix of GPS location and of the 3GPP mobile systems used as “data pipes”.
However, such an approach presents fundamental technology limitations from the point of view of e.g. device battery life (due to the extensive GPS usage), signaling load to the network (due to the required uplink bursty traffic) and simplicity (due to the “proactive” behavior required of the user, e.g. the “check in”).
While the use of an unlicensed-spectrum communication can address some of the aspects mentioned earlier, it still presents some limitations. For example, discovery processes are being defined based on direct message exchanges and thus not optimal for operation over longer ranges (hundreds of meters or more), or preserve a reasonable battery life. For the same reason, an unlicensed option cannot be expected to scale among a large number of devices.
For future cellular communication networks, a possible method for such proximity-based applications and services is the so-called device-to-device (D2D) communication. D2D offers a high communication speed, large capacity and a high quality of service which are important features to be achieved. Advantages achievable by the implementation of D2D communications in the cellular communication environment are, for example, an offloading of the cellular system, reduced battery consumption due to lower transmission power, an increased data rate, an improvement in local area coverage robustness to infrastructure failures and also an enablement of new services. This is possible while also providing access to licensed spectrum with a controlled interference environment to avoid the uncertainties of license exempt band. Due to this, D2D communication gains more and more attraction and interest.
However, in order to make a D2D communication applicable to communication networks, such as those based on 3GPP LTE systems, it is necessary to evolve a suitable platform in order to intercept the demand of proximity-based applications so that it is possible that devices, such as UEs or the like, can discover each other directly over the air, and potentially communicate directly, wherein a certain level of control for the network operator side has to be maintained so that D2D communication makes sense from a system management point of view.
For example, if a device (such as a UE) uses simultaneously licensed (i.e. cellular) and unlicensed spectrum, e.g. via inter-band carrier aggregation methods it is required to enable the network, i.e. a communication network control element (such as an eNB) which schedules transmission over the licensed spectrum and allocates also the necessary resources, to conduct a suitable control balancing the actual need of resources of the device in question and the totally available resources in particular at the licensed spectrum.